Field of the Invention
This invention relates to liquid color used to color molded and extruded plastic parts during fabrication thereof, and more particularly relates to diaphragm pumps for pumping liquid color, and even more specifically to diaphragm pumps for pumping liquid color where the pump is equipped with a quick release mechanism so that the pump can be quickly removed from a container of liquid color to which the pump is attached, for rapid changeover when the liquid color container is empty, or a change in color is desired.
Description of the Prior Art
Pumps for liquid color are known, with one such pump being disclosed in U.S. Pat. No. 7,416,096, with another being disclosed in U.S. Pat. No. 7,980,834, and yet another being disclosed in U.S. Pat. No. 8,800,821. The disclosures of U.S. Pat. Nos. 7,416,096, 7,980,834, and 8,800,821 are hereby incorporated by reference.
The '096 patent discloses a container of liquid color material having a diaphragm liquid color pump located in the container for providing liquid color from the container. The diaphragm liquid color pump is located in the container at the container bottom, where the pump can collect liquid color as the container empties. The pump is driven by a pneumatic piston-cylinder combination located outside the container, with a shaft extending downwardly from the pneumatic piston-cylinder combination to the diaphragm pump, to reciprocate the diaphragm back and forth to effectuate pumping action.
The apparatus disclosed in '096 is relatively low in cost. The apparatus includes a liquid-tight fitting allowing the liquid color output from the pump to be supplied directly to a plastics material processing machine, for the liquid color to impart color directly to plastic parts as they are manufactured.
The '834 apparatus provides pressure boosting, permitting liquid color to be injected into an extruder screw or a molding machine screw barrel at a position downstream from the throat, closer to the position at which the finished plastic parts are molded or extruded.
The '821 patent discloses a disposable low-cost pump in a container for liquid color, where the pump is fabricated from a plurality of PVC tubular members connected in a way to provide a pumping chamber. A piston is displaceable into the pumping chamber. A spring biases the piston outwardly from the chamber, in opposition to force applied by an air cylinder.
While these devices all have merit and all have proved commercially successful, there is a continuing need for even lower cost, even higher reliability apparatus to provide liquid color from liquid color containers to injection and compression molding machines and to extruders, to color plastic parts in the course of manufacture thereof. Moreover, there is a need to regulate flow of liquid color by regulating the pump in order to provide the most accurate flow of liquid color into the molding machine or extruder.
While disposable pumps for liquid color are known in the sense that those pumps can be removed from the liquid color containers and discarded, there is a need for a pump that fits integrally with a liquid color container in a manner to be a part of the container so that the complete, assembled pump cannot be removed without compromising the container and leaving an open hole. This is to discourage pump scavenging.
There is a further need, which is somewhat inconsistent with the foregoing, for the relatively high cost portions of the pump to be easily and quickly removable once the container has been emptied, so that those high cost portions of the pump may be used with a new, full container of liquid color, while low cost portions of the pump remain with an empty container to prevent flow of any remaining liquid color out of the container, and may be used when the container is refilled and the pump is reassembled to pump liquid color from the new container.